Question

characteristics features of dinoflagellates​

Answer 1

Explanation:

They are planktonic.

Ninety percent of all dinoflagellates are marine plankton. Others are benthic, symbiotic, or parasitic.

They are small.

Although many of them are microscopic and range from 15 to 40 microns in size, the largest,Noctiluca, may be as large as 2 mm in diameter!

They are motile.

Dinoflagellates swim by means of two flagella, movable protein and microtubule strands that propel the cell through the water. The longitudinal flagellum extends out from the sulcal groove of the hypotheca (posterior part of cell); when it whips back and forth it propels the cell forward. The flattened transverse flagellum lies in the cingulum, the groove that extends around the equator of the cell. Its motion provides maneuvering and forward movement. As a result of the action of the two flagella the cell spirals as it moves.

Many are thecate, having an internal skeleton of cellulose-like plates.

The cortical (outer) part of the cell contains flattened vesicles known as alveoli. In “armored” species, polysaccharide deposited in the vesicles forms rigid plates called thecae. “Naked” cells lack thecae.

Their chromosomes are always condensed.

Dinoflagellate DNA always exists in a crystalline form in the nucleus, unlike other eukaryotes. In addition, lack proteins called histones that in other eukaryotic cells helps organize the chromosomes. Dinoflagellates contain a lot of DNA, which explains the large size of the nucleus. The metabolic requirements of supporting the large amount of DNA may explain the low growth rates of dinoflagellates compared to other unicellular protists.

Not all dinoflagellates are photosynthetic.

Many dinoflagellates are photosynthetic, manufacturing their own food using the energy from sunlight, and providing a food source for other organisms. The photosynthetic dinoflagellates are important primary producers in coastal waters. Some photosynthetic dinoflagellates are symbiotic, living in the cells of their hosts, such as corals. Called zooxanthellae, they are found in many marine invertebrates, including sponges, corals, jellyfish, and flatworms, as well as within protists, such as ciliates, foraminiferans, and colonial radiolarians. Approximately half of all species are heterotrophic, eating other plankton, and sometimes each other, by snaring or stinging their prey. Non-photosynthetic species of dinoflagellates feed on diatoms or other protists (including other dinoflagellates); Noctiluca is large enough to eat zooplankton and fish eggs. Some species are parasites on algae, zooplankton, fish or other organisms.

Answer 2

Dinoflagellates

$\bigstar$ They are golden brown photosynthetic protists.

$\bigstar$ These are mostly marine and photosynthetic forms.

$\bigstar$ They appear yellow, green, brown, blue or red depending on the main pigments present in their cells.

$\bigstar$ The cell wall has stiff cellulose plates on the outer surface called thecalories.

$\bigstar$ The theca contains two grooves the longitudinal groove called the sulcus and the transverse groove known as the cingulum or annulus or girdle.

$\bigstar$ Reserve food is stored in the form of starch in fresh water forms and oils in marine forms.

$\bigstar$ Most of them have two unequal flagella (heterokont). One long flagellum lies vertically in sulcus the other short flagellum arranged perpendicular to long flagellum in transverse groove.

$\bigstar$ Due to presence of two flagella at night angles to each other, the dinoflagellates show peculiar spinning movement. Hence they are called hiring whips.

$\bigstar$ Very often, red dinoflagellates undergo such rapid multiplovation that they make the tide appear red.

Example :- Gonyaulax.